High-performance multi-megahertz optical coherence tomography based on amplified optical time-stretch.

Jingjiang Xu,Luoqin Yu,Chi Zhang,Xiaoming Wei,Jianbing Xu,Kevin K Tsia,K K Y Wong

doi:10.1364/boe.6.001340

Abstract

As the key prerequisite of high-speed volumetric structural and functional tissue imaging in real-time, scaling the A-scan rate beyond MHz has been one of the major pursuits in the development of optical coherence tomography (OCT). Along with a handful of techniques enabling multi-MHz, amplified optical time-stretch OCT (AOT-OCT) has recently been demonstrated as a viable alternative for ultrafast swept-source OCT well above MHz without the need for the mechanical wavelength-tuning mechanism. In this paper, we report a new generation of AOT-OCT demonstrating superior performance to its older generation and all other time-stretch-based OCT modalities in terms of shot-to-shot stability, sensitivity (~90dB), roll-off performance (>4 mm/dB) and A-scan rate (11.5 MHz). Such performance is mainly attributed to the combined contribution from the stable operation of the broadband and compact mode-locked fiber laser as well as the optical amplification in-line with the time-stretch process. The system allows us, for the first time, to deliver volumetric time-stretch-based OCT of biological tissues with the single-shot A-scan rate beyond 10 MHz. Comparing with the existing high-speed OCT systems, the inertia-free AOT-OCT shows promises to realize high-performance 3D OCT imaging at video rate.

Highlights

Well-recognized for its capability of label-free in-vivo deep-tissue (>1mm) imaging in threedimensional (3D) with micrometer-resolution (~10 μm or less), optical coherence tomography (OCT) is continuously gaining popularity in clinical diagnostics
(2) It enables functional OCT with high spatiotemporal resolution, e.g. Doppler OCT [15] and OCT-based angiography [16], which commonly require image computation based on multiple frames to visualize the vasculatures in 3D. (3) It is essential for imaging requiring high-density sampling as ultrafast A-scan rate helps reducing the frame acquisition time and minimizing the image distortion due to motion artifacts
We present a new generation of amplified optical time-stretch OCT (AOT-OCT) system which shows a significant improvement in sensitivity (~90dB) at an even higher A-scan rate of >10MHz

Summary

Introduction

Well-recognized for its capability of label-free in-vivo deep-tissue (>1mm) imaging in threedimensional (3D) with micrometer-resolution (~10 μm or less), optical coherence tomography (OCT) is continuously gaining popularity in clinical diagnostics. We have recently demonstrated broadband amplified optical time stretch OCT (AOT-OCT) which achieved 7.14 MHz fundamental A-scan rate over 80 nm bandwidth with a sensitivity of >80 dB [28]. While this was the first demonstration of applying time-stretch-based OCT for invivo biological specimen imaging, the sensitivity and the image quality is yet to be satisfactory for practical research and clinical applications. Owing to the simple and compact broadband fiber laser configuration as well as the all-optical passive ultrafast wavelength-swept mechanism, the AOT-OCT system presented here is an attractive alternative for practical multi-MHz OCT and video-rate 3D OCT if high-throughput data acquisition is available

Experimental implementation

Laser source performance

Discussion

Conclusion